Rotor shroud



Dec. 25, 1962 y J. D. STEWART 3,070,350

Ro'roR SHROUD Filed June 2, 1958 5 Sheets-Shlelet 1 Dec. 25, 1962 J. D. .STEWART 3,070,350 l ROTOR SHROUD Filed June 2. 1958 5 Sheets-Sheet 2 Dec. 25, 1962 J. D. STEWART ROTOR SHROUD 5 Sheets-Sheet 5 INVENTOR.

Dec. 25, 1962 J. D. STEWART 3,070,350

ROTOR SHROUD Filed June 2. 1958 5 Sheets-Sheet 4 N VEN TOR. (@fewff Dec. 25, 1962 J. D. STEWART RoToR sHRoUD United States Patent 3,070,350 ROTOR SHROUD Jim D. Stewart, Indianapolis, ind., assignor to General VVMotors Corporation, Detroit, Mich., a corporation of Delaware Filed June 2, 1,958, Ser. No. 740,988

2 Claims. (Cl. 253-77) My invention relates to the rotors of turbomachines, particularly axial flow compressors, and more specifically to an improved shrouded rotor structure.

It is known that the efficiency of axial flow compressors may be improved by providing a shroud ring extending around the outer ends or tips of the rotor blades. The provision `of such a shroud involves considerable difficulty, particularly with rotors of large diameter having long blades. In such a case, the tips of the blades are rather widely spaced and, since the structure rotates at high speed, the centrifugal force on the shroud is quite high. It is particularly important, in some cases, to keep the structure of the compressor as light as possible; and, if' the shroud is heavy, it not only contributes unnecessary weight directly but may require a heavier disk to withstand the centrifugal force.

It is also important that the shroud structure be such that the blades may be removed individually from the rotor in case of damage to a blade. The present invention provides a lightweight shroud structure which is easily attached to and removed from the blades and which is strong and secure.

The principal objects of the invention are to improve the performance of turbomachines such as compressors, and to provide an improved shrouded rotor structure. The invention is described herein in terms of two embodiments in axial ow compressors to illustrate the principles thereof.

The nature of the invention and the advantages thereof will be clear to those skilled in the art from the succeed.- ing detailed description of preferred embodiments of the invention and the accompanying drawings thereof.

FIGURE l is a fragmentary rear view, with parts in section, of a compressor rotor stage embodying a rst form of the invention, the view being taken in a plane perpendicular to the axis of the rotor.

FIGURE 2 is a fragmentary plan view of the shroud and blade taken on the plane indicated by the line 2--2 in FIGURE 1,

FIGURE 3 is a sectional view taken on the plane indicated by the line 3-3 in FIGURE 2.

FIGURE 4 is a sectional view taken on the plane indicated by the line 4-4 in FIGURE 2. f FIGURE 5 is an exploded view of the blade and shroud structure of FIGURE l.

' FIGURE 6 is a view similar to that of FIGURE 2 of'a second embodiment of the invention.

FIGURE 7 is a sectional view taken on the plane indicated by the line 7-7 in' FIGURE 6.

j FIGURE 8 is a sectional view taken on the plane indicated bythe line 8--8 in FIGURE 6.

FIGURE A9 is a partially exploded view of the shroud structure of FIGURE 6.

Referring first to FIGURE l, which sufficiently illustrates a'compressor rotor structure to explain the invention', the rotor comprises a rotor disk or wheel 10,` only the periphery of which is illustrated. The wheel comprises a rim 11 having dovetail slots 12 therein extending across the rim or, in other words, axially of the rotor. A ring or row of blades 13 are mounted in the rim of the rotor. Each blade comprises an airfoil or blade portion 14, a platform 15, a stalk 16, and a root 17 which is configured to fit the dovetail slot 12. Since the platform rice and blade are of greater axial extent or .chord than the root, generally triangular webs 18 extend from the faces of the root and stalk to the underside of the platform. The blade platforms engage along their edges to Provide a conical ring which is the inner boundary of the flow path through the compressor. An interrupted air baie ange 19 extends outwardly from the rim 1-1 between the stalks to the inner surface of the platforms 15.

It will be noted that the blades are long and widely spaced at the tip or free end thereof and that the free ends are disposed at a considerable angle, or skewed, to the rotor axis, which is perpendicular to the plane of FIG.- URE l.

The structure so far described merely constitues the environment for the improved shroud structure which may, of course, be employed with blades mounted in vari!r ous ways on rotors of various structures.

Referring also to FIGURES 2 to 5, the outer or free ends of the blades mount a rotor shroud or shroud ring 20 which consists of a number of segments 21, each segment extending from the free end of one blade to the free end of the next. The shroud segments are connected to the blade by an arrangement similar to a three-part hinge, the general nature of which will be apparent from FIGURE 5. The free end of the blade portion 14 has integral therewith a small shelf or platform 22 extending from edge to edge of the blade. A number of projections' 23 integral with the blade extend outwardly from the shelf 22 and are bored to provide a row of aligned holes 24 through the projections. A cylindrical pin 26 may 'be inserted through the holes 24.

Each shroud segment 21 is a one-piece forging, the cross section of which is most clearly shown in FIGURE 4. It consists of a curved plate or base 27 with ribs k28 extending radially from it near the edges and a central rib 29. Flanges 31 extend generally parallel to the base 27 adjacent the outer edges of ribs 28. Flanges 32 extend across each end of the segment and outwardly from the outer surface thereof. A number of generally rectangular projections 33 having aligned holes 34 therein extend from each ange 32. As shown clearly in FIGURE 2, the flange 32 extends parallel to the direction of the shelf22 and the projections 33 are spaced to abut one side of the projections 23. In other words, the projections'33 on the adjoining ends of two adjacent shroud sections fit between the projections 23 on the blade, and the pin 26 extends through the holes 24 and 34 to provide, a strong connec.- tion between the blade and shroud. The width of the projections is such that there is no significant play inthe direction axially of the pin. 1 r

The ends of the flanges 31 extend approximately t0 the `center line of the pin so that a substantially continuous shroud is provided by the segments meeting along the Ime 36 in FIGURE 2. The outboard lor end portions 37 of the shelf 22 are aligned with the marginal-portions 38 of the base 27 of the shroud. The shroud and bladestruc.- ture therefore provides two axially projecting flanges on each face of the shroud. These flanges as well as ,the ribs 28 and 29 may cooperate with fixed structure in the compressor (not illustrated) to provide a labyrinth seal.

A projection or abutment 41 extending from one end Of each segment 21 provides a stop against which one end of pin 26 Ylodges when it is inserted. The pin is held against sliding out in the other direction by adeformable retainer 42, which, before the pin is inserted, is simply a small metal sheet bent at a right angle to provide a leg 43 extending between the end projection 23 on the blade and the adjacent projection 33. The retainer leg 43 has a hole through which the pin extends. The other or free end of the retainer lies alongside the face of end flange 32 of a shroud segment. After the pin has been inserted,

Patented Dec. 25, 1.962'

the end 46 of the retainer is bent over as indicated by the broken lines in FIGURE and by the solid lines in FIGURE 3 so as to overlie the end of the pin 26 and hold it against sliding out.

FIGURES 6 to 9 depict a second form of the invention which differs from that previously described only in the structure of the shroud segments. The shroud segments of FIGURES 6 to 9, except for the parts which connect them to the blade, are brazed fabricated sheet metal structures rather than forgings as in FIGURE 1. Since the blade of the second form may be identical to that previously described and likewise the structure by which the shroud segments are connected to the blades, these need not be described again. The sheet metal shroud segment of FIGURE 7 may have a higher stiffness or lighter weight than the forged shroud segment, but is more complicated from the standpoint of fabrication.

Referring to FIGURES 6 to 9, the shroud segment 51 comprises a body or major part 52 to each end of which are xed connecting pieces 53 having projections 54. The connecting pieces, as will be apparent particularly from FIGURE 9, are substantially the same as the end flanges 32 of the previously described form. The body 52 of the segment comprises an inner band 56, an outer band 57, and a rectangularly sinuous strip 58 mounted between and brazed to the bands 56 and 57. As will be apparent particularly from FIGURE 7, the sinuous strip defines a number, preferably six, of radial webs 59 which are joined by axially extending webs alternately brazed to the bands 56 and 57. Shallow flanges 61 and 62 at the edges of bands 56 and 57 may serve for sealing purposes and also for some stiiening function.

Each segment is slightly curved so that the ring of segments is circular. The ends 63 of the webs 59 extend beyond the axially extending portions of strip S8 and are bent over to form a substantially continuous end surface.

The ends of the inner and outer bands 56 and 57 project beyond the bent over ends 63 and the base 64 of the connecting piece 53 lits into the channel thus defined and is brazed to the ends 63 and the ends of the inner and outer bands. The base 64 is provided with spaced lightening holes 66 which extend through the base between the projections 54 and at the ends of thebase. The outer band 57 has six holes 67 in it overlying the upper surfaces 68 of the strip 58 to which strip 57 is bonded, provided for inspection of the brazed connection of band 57 to strip 58.

It will be understood that the ends of the upper band 57 extend so as substantially to meet along the line 71 radially outwardly of the pin 26, as shown at the right in FIGURE 6. The pin is retained by an abutment 41 and a retainer 42, as previously described.

It will be seen that the two forms of shroud segment are functionally similar and that either might be adopted. Each has certain advantages in terms of fabrication and weight, depending upon the particular requirements of the installation. It will be apparent that either structure provides a strong lightweight rotor shroud which is easy to apply and remove and is very securely retained on the blades. v

The description of preferred embodiments of the invention for the purpose of explaining the principles thereof is not to be considered as limiting the invention, since many modifications may be made by the exercise of skill in the art within the scope of the invention.

What is claimed is:

1. A turbomachine comprising, in combination, a rotor, a row of blades mounted on and extending from the rotor,

CTI

the blades terminating in free ends, and a rotor blade shroud comprising a ring of shroud segments mounted end-to-end, each segment extending from the free end of a blade to the free end of a blade next adjacent thereto, two shroud segments being connected to the free end of each blade, each blade having a plural number of aligned spaced projections extending outwardly from the free end thereof, each shroud segment having a plural number of aligned spaced projections extending from each end thereof, the projections on each blade and on the shroud segments adjacent thereto intertting in aligned relation and the projections having holes therethrough aligned when the shroud segments are in assembled relation to the blade, and a hinge pin extending through the said holes at the free end of each blade to couple the shroud segments to the blade, each shroud segment being a fabricated assembly comprising an outer band, an inner band, a substantially rectangular sinuous strip bonded to and between the bands, the strip having radially and circumferentially extending webs with the ends thereof extending transversely of the shroud, and connecting pieces bearing the said projections bonded to the said transversely extending ends.

2. A turbomachine comprising, in combination, a rotor, a row of blades mounted on and extendingfrom the rotor, the blades terminating in free ends, and a rotor blade shroud comprising a ring of shroud segments mounted end-to-end, each segment extending from the free end of a blade to the free end of a blade next adjacent thereto, two shroud segments being connected to the free end of each blade, each blade having a plural number of aligned spaced projections extending outwardly from the free end thereof, each shroud segment having a plural number of aligned spaced projections extending from each end thereof, the projections on each blade and on the shroud segments adjacent thereto intertting in aligned relation and the projections having holes therethrough aligned when the shroud segments are in assembled relation to the blade, a readily removable hinge pin extending through the said holes at the free end of each blade to couple the shroud segments to the blade, a xed stop on a segment engaging one end of each hinge pin, and a pin retainer engaging the other end of the pin, the pin retainer having one end inserted between two of the projections, said end having a hole for the pin, the pin extending through the hole in the retainer and the other end of the retainer being deformable into overlying relation to the other end of the pin.

References Cited in the le of this patent UNITED STATES PATENTS 1,876,067 Lorengen a Sept. 6, 1932 1,998,951 Downer Apr. 23, 1935 2,220,914 Robinson Nov. 12, 1940 2,220,918 Smith Nov. 12, 1940 2,221,684 Smith Nov. 12, 1940 2,315,610 Flanders Apr. 6, 1943 2,315,612 Franck Apr. 6, 1943 2,366,142 Allen Dec. 26, 1944 2,625,366 Williams Jan. 13, 1953 2,801,789 Moss Aug. 6, 1957 2,959,393 Rankin Nov. 8, 1960 2,971,743 Welsh Feb. 14, 1961 FOREIGN PATENTS 532,358 Great Britain Ian. 22, 1941 740,757 Great Britain Nov. 16, 1955 

